Hub clutch assembly

ABSTRACT

A hub clutch assembly mounted between an axle and a hub of a four-wheel drive vehicle and having a 2WD/4WD position indicator that is simple in structure. A slide ring is axially slidably mounted on the axle. The slide ring is biased by a spring to a position in which an external gear formed on the slide ring engages an internal gear of an outer ring to maintain 4WD position. A magnet fixed to a cover attracts the slide ring to a 2WD position and keeps it in the 2WD position. The drive mode is changed between the 2WD mode and the 4WD mode by supplying pressure fluid only for a limited time period set by timers. A pressure gauge is provided in a passage for pressure fluid to indicate whether the current drive mode is the 2WD mode or the 4WD mode.

BACKGROUND OF THE INVENTION

This invention relates to a hub clutch assembly for selectivelytransmitting driving force between a wheel axle and a wheel hub, andmore particularly a hub clutch assembly having a four-wheel drive modeindicator means that is simple in structure.

A part-time four-wheel drive vehicle has hub clutches mounted betweenthe front wheel hubs and the front axle to selectively transmit torquebetween the wheels and the axle.

A conventional such hub clutch has an axially slidable slide gearmounted on the axle. By engaging this gear with the wheel hub, the axleis rigidly coupled to the wheel hub (4WD mode). By disengaging the slidegear, the axle is disconnected from the wheel hub (2WD mode). Fluidpressure such as air pressure is used to move the slide gear between the2WD and 4WD positions.

Such a hub clutch assembly has to have an indicator means which cannotify the driver behind the wheel whether the drive mode is now in the2WD or 4WD position.

Such a drive mode or position indicator is disclosed in unexaminedJapanese patent publication 1-186434 and comprises sensors for detectingthe 2WD and 4WD positions of the slide gear moved by pressure fluid, andan indicator means electrically connected to the sensors for indicatingwhether the current drive mode is in the 2WD or 4WD position.

Such sensors are extremely complicated in structure and expensive tomanufacture.

An object of this invention is to provide a hub clutch assembly having a2WD/4WD position indicator means that is simple in structure andincludes a pressure detector for detecting a negative pressure used tochange the drive mode.

SUMMARY OF THE INVENTION

According to this invention, there is provided a hub clutch assemblycomprising a driving member coupled to an axle, a driven member coupledto a wheel hub, the driving member and the driven member being rotatablymounted one around the other, a control means for selectively couplingand disengaging the driving and driven members by supplying pressurefluid, and a pressure gauge provided in a passage of the pressure fluidused to selectively couple and disengage the driving and driven membersfor detecting whether the driving and driven members are coupledtogether or disengaged from each other.

According to the invention there is also provided a hub clutch assemblywherein the pressure fluid for selectively coupling and disengaging thedriving and driven members is supplied through two passages connected totwo respective airtight chambers provided between the driving and drivenmembers, wherein timer-activated valves are provided to selectivelysupply the pressure fluid into the two passages or discharge pressurefluid from the two passages, and wherein a pressure gauge is provided inat least one of the two passages.

Pressure fluid is supplied only while the driving mode is being changedbetween 4WD and 2WD positions for a limited time period set by timers.Once the driving mode changes, pressure fluid is released to bring thepressure in the airtight chambers back to the atmospheric pressure. 4WDposition is maintained by the elastic force of a spring whereas 2WDposition is maintained by attracting the slide ring to the magnet fixedto the cover. The pressure gauge measures the pressure during the drivemode change phase. When it detects a pressure necessary for drive modechange, it indicates that the drive mode has changed from 4WD to 2WD orfrom 2WD to 4WD.

Other features and objects of the present invention will become apparentfrom the following description made with reference to the accompanyingdrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of layout of a 4WD vehicle having hub clutches;

FIG. 2 is a vertical sectional view of a hub clutch assembly mounted ona 4WD vehicle in the 2WD position;

FIG. 3 is an enlarged vertical section of the hub clutch assembly ofFIG. 2 in the 4WD position;

FIG. 4 shows a control device in the 2WD position;

FIG. 5 shows the control device of FIG. 4 when the drive mode is beingchanged from 2WD to 4WD position;

FIG. 6 shows the control device of FIG. 4 when the drive mode is beingchanged from 4WD to 2WD position; and

FIG. 7 is a flowchart of the operation of the control device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of this invention is described with reference to thedrawings.

FIG. 1 shows the power train of an FR-based 4WD on which are mounted hubclutches 1 between the front wheels and both ends of the front wheelaxle.

FIGS. 2 and 3 show one embodiment of hub clutch 1. The front axle 2 isactually a shaft of a constant velocity joint 3 coupled to the vehiclepower train. Mounted on the axle 2 is a spindle 4 fixed to a vehicleknuckle 5 and rotatably supporting a wheel hub 8 through a bearing 6.

The hub clutch 1 has a slide ring 9 as a driving member nonrotatably butaxially slidably mounted on the end of the axle 2 through serrations 10.The slide ring 9 carries on its outer periphery an external gear 24. Anouter ring 13 as a driven member is rotatably mounted around the slidering 9. The outer ring 13 has its rear end fixed to an end face of thewheel hub 8 by bolts 14. The outer ring 13 has on its inner periphery aninternal gear 25 adapted to mesh with the external gear 24.

The outer ring 13 has its outer end closed by a cover 26a integral withthe ring 13. A diaphragm 27a has its outer edge airtightly fixed to theinner periphery of the outer ring 13 and its radially inner portionjoined to the slide ring 9 so as to be axially movable together with thering 9 while maintaining airtightness therebetween. The diaphragm 27athus partitions the interior of the outer ring 13 into two airtightchambers 29 and 30.

A spring 31 is mounted between the opposed faces of the diaphragm 27aand the cover 26a in a compressed state, thus biasing the slide ring 9rearwardly toward its back position. A magnet 33 is fixed to the innerface of the cover 26a at its center through a case 32. When the slidering 9 is in its front position in which the external gear 24 is not inmesh with the internal gear 25, the magnet 33 attracts a metal fixingpiece 27b of the diaphragm 27a, thus keeping the ring 9 in its frontposition.

In order to change the driving mode between a two-wheel and a four-wheeldrive position, air passages 34 and 35 communicate with the airtightchambers 30 and 29, respectively.

The first air passage 35 comprises a passage 35b formed in the outerring 13 and communicating with the outer airtight chamber 29, a gap 35cbetween the spindle 4 and the wheel hub 8, and a passage 35d formed inthe rear end of the spindle 4 so as to communicate with the gap 35c andthe gap in the bearing 6 mounted in the gap 35c. The passage 35d isconnected to an air pipe 58 connected to an air source, which will bedescribed later.

The second air passage 34 communicating with the inner airtight chamber30 comprises a gap 34b between the front wheel axle 2 and the spindle 4,and a passage 34c formed in the spindle 4 near its rear end so as tocommunicate with the gap 34b. The passage 34c is connected to an airpipe 57 connected to the air source.

The airtight chambers 29 and 30 are kept airtight by an oil seal 42mounted between a nut 41 threaded onto the tip of the spindle 4 and theinner periphery of the outer ring 13. Since the first passage 35 ismostly the gap between the spindle 4 and the wheel hub 3, and the secondpassage 34 is mostly the gap between the front wheel axle 2 and thespindle 4, the formation of such passages barely increases the diameterof the hub clutch 1.

Now in operation, in order to change the drive mode to the 4WD position,the slide ring 9 is moved inwardly to bring the external gear 24 intomesh with the internal gear 25.

In this state, the front axle 2 and the outer ring 13 are directlycoupled together, so that all four wheels are now coupled to the engine.This means that the engine brake is distributed to all the wheels.

To change the drive mode from 4WD to 2WD, air drawn out of the outerairtight chamber 29. The negative pressure thus created in the chamber29 acts on the diaphragm 27a, so that the slide ring 9 is pulledoutwardly against the force of the spring 31 until the external gear 24disengages from the internal gear 25 as shown in FIG. 2.

Thus, by selectively creating a negative pressure in either of theairtight chambers 29 and 30, the drive mode can be changed between 2WDand 4WD. The magnet 33 attracts the diaphragm 27a to keep the 2WDposition. The spring 31 maintains the 4WD position.

FIG. 4 shows a control device connected to the first and second airpassages 34, 35 for controlling the position change of the slide ring 9between 2WD and 4WD.

The control device includes a negative pressure source 51 which may bethe engine intake manifold, a pump or a compressor. Connected to thenegative pressure source 51 is a negative pressure pipe 52 provided witha check valve 53 and a negative pressure tank 54 and having bifurcatedlines connected to first and second electromagnetic valves 55 and 56,respectively.

If the negative pressure source 51 is the intake manifold, the manifoldcannot create a negative pressure while the engine is being accelerated.In this case, a negative pressure is supplied by the negative pressuretank 54.

The first electromagnetic valve 55 is used to change the drive mode from2WD to 4WD. The first pipe 57 has its one end connected to one port ofthe electromagnetic valve 55 and the other end thereof connected to thesecond air passage 34 of each hub clutch 1 at its passage 34c formed inthe spindle 4 near its rear end.

The second electromagnetic valve 56 is used to change the drive modefrom 4WD to 2WD. The second pipe 58 has one end thereof connected to oneport of the valve 56 and the other end thereof to the first air passage35 of each hub clutch 1 at its passage 35d formed in the spindle 4 nearits rear end.

Each of the electromagnetic valves 55, 56 has an outlet port whichcommunicates with the atmosphere through a pipe 59. When energized, thevalve 55 assumes a position in which the negative pressure pipe 52communicates with the first pipe 57. When deenergized, the valve 55assumes a position in which the negative pressure pipe 52 isdisconnected from the first pipe 57, and the first pipe 57 communicateswith the pipe 59.

When the second valve 56 is energized, the negative pressure pipe 52communicates with the second pipe 58. When it is deenergized, thenegative pressure pipe 52 is disconnected from the second pipe 58, andthe second pipe 58 communicates with the pipe 59.

The electromagnetic valves 55 and 56 are connected to a power source 60through a hub lock switch 61. A first timer 62 and a second timer 63 areprovided in the lines between the switch 61 and the respective valves55, 56. When the position of the switch 61 is changed, one of the valves55, 56 is energized and a negative pressure is applied to the diaphragm27a for a time period determined by the respective timer 62, 63.

A pressure gauge, or a negative pressure gauge 71 to be exact, isprovided in the first pipe 57 connected to the negative pressure pipe 52through the first electromagnetic valve 55. The gauge 71 indicateswhether the current drive mode is the 2WD mode or the 4WD mode.

FIG. 7 shows the flowchart of the operation of the control deviceprovided with the negative pressure gauge 71, which measures thenegative pressure created in the airtight chamber 30 when the drive modeis changed from 2WD to 4WD. If the negative pressure reading on thegauge is smaller than the minimum negative pressure (e.g. -260 mm Hg)necessary to move the slide ring 9 from the 2WD to 4WD position, thegauge 71 turns on the lock indicator 72 to indicate that the drive modeis now the 4WD mode. If it is higher than that, the gauge 71 turns offthe lock indicator 72 to indicate that the drive mode is the 2WD mode.

Needless to say, the lock indicator 72 has to be arranged at a positionwhere the driver at the driver seat can see it. Two negative pressuregauges may be provided in the first pipe 57 and the second pipe 58,respectively.

Now in operation, during 2WD mode shown in FIG. 2, the metal piece 27bof the diaphragm 27a is attracted to the magnet 33 while compressing thespring 31. Thus, the slide ring 9 is at the outer position, with theexternal gear 24 disengaged from the internal gear 25.

In this state, the front wheel axle (driving ember) is disconnected fromthe wheel hub (driven ember) and, no torque is transmitted from thewheel hub to the axle.

Since the front axle 2 is disconnected from the engine by the transferin this state, no driving force is transmitted to the front axle 2either from the engine or the wheels. Thus, the drive train from thetransfer to the front axle stops during 2WD mode.

FIG. 4 shows the control device during 2WD mode. The first and secondelectromagnetic valves 55, 56 are both deenergized, so that their spoolsshut off communication between the negative pressure pipe 52 and thefirst and second pipes 57, 58. Thus, the first and second air passages34, 35, as well as the airtight chambers 29, 30, are at the atmosphericpressure.

To change the drive mode from 2WD to 4WD, the transfer is changed fromthe 2WD position to the 4WD position with the ignition switch 73 on asshown in FIG. 7. This automatically causes the hub lock switch 61 tochange from 2WD to 4WD position as shown in FIG. 5, energizing the firstelectromagnetic valve 55 connected to the switch 61 through the timer62. The negative pressure pipe 52 is now brought into communication withthe first pipe 57, so that the negative pressure produced in thenegative pressure source 51 is applied to the inner airtight chamber 30through the first pipe 57 and the second air passage 34. The negativepressure in the first pipe 57 is thus detected by the negative pressuregauge 71.

When the air in the airtight chamber 30 is drawn out under a negativepressure lower than a predetermined level through the second air passage34, a negative pressure acts on the diaphragm 27a, pulling the slidering 9 inwardly away from the cover 26 in cooperation with the force ofthe spring 31 against the attracting force of the magnet 33 until theexternal gear 24 engages the internal gear 25 of the outer ring 13. Thedrive mode now shifts to 4WD position. During the 4WD mode, engine brakecan be applied to both front and rear wheels.

By applying a negative pressure lower than the predetermined level, itis possible to change the drive mode with high reliability. The negativepressure gauge 71 turns on the lock indicator 72 to notify the driverthat the drive mode is now the 4WD mode.

When a predetermined time determined by the timer 62 has passed, thefirst electromagnetic valve 55 is deenergized, so that the communicationbetween the negative pressure pipe 52 and the first pipe 57 is shut off,and the first pipe 57 is brought into communication with the pipe 59.The pressure in the airtight chamber 30 thus rises to the atmosphericpressure.

To change over the drive mode from 4WD to 2WD mode, the transfer mode isshifted from 4WD to 2WD mode. This automatically shifts the hub lockswitch 61 from 4WD to 2WD position as shown in FIG. 6, thus energizingthe second electromagnetic valve 56 connected to the switch 61 throughthe second timer 63. The negative pressure pipe 52 is now brought intocommunication with the second pipe 58, so that the negative pressureproduced in the negative pressure source 51 is applied to the outerairtight chamber 29 through the second pipe 58 and the first air passage35.

The negative pressure created in the outer airtight chamber 29 pulls thediaphragm 27a and the slide ring 9 outwardly against the force of thespring 31 until the metal piece 27b of the diaphragm 27a is attracted tothe magnet 33. The external gear 24 is now disengaged from the internalgear 25.

After a predetermined time, the second timer 63 deenergizes the secondelectromagnetic valve 56 to shut off communication between the negativepressure pipe 52 and the second pipe 58 and bring the second pipe 58into communication with the pipe 59. The pressure in the airtightchamber 29 thus rises to the atmospheric pressure. The negative pressuregauge 71 detects the atmospheric pressure, which is higher than thepredetermined negative pressure, thus turning off the lock indicator 72to notify the driver that the drive mode is now in 2WD position.

As described above, the drive mode can be changed by selectivelycreating a negative pressure in the airtight chambers 29 and 30partitioned by the diaphragm 27a. The 2WD position is maintained byattracting the metal piece 27b of the diaphragm 27a to the magnet 33.The 4WD position is maintained by the force of the spring 31.

Thus, once the ring 9 is moved to the 2WD or 4WD position, there is noneed to keep creating a negative pressure in either of the chambers 29,30. That is, the pressure in the chambers 29 and 30 can be brought backto the atmospheric pressure. Thus, hub seals, spindle seals and sealrings 28 are subjected to negative pressures only for a short period oftime. This extends the life of these members.

The timers 62 and 63, as well as the electromagnetic valves 55 and 56,are never activated simultaneously. If the hub lock switch 61 is changedwhile one of the valves and the corresponding timer are energized, thisvalve and the corresponding timer are deenergized and the other valveand the corresponding timer are now energized.

In the illustrated example, the negative pressure gauge 71 is providedin the first pipe 57 to detect change from 2WD to 4WD. But instead, itmay be provided in the second pipe 58 to detect change from 4WD to 2WDto indicate the 4WD position.

According to this invention, a negative pressure gauge is provided in anair passage for a negative pressure fluid for changing the drive modebetween the 2WD mode and the 4WD mode to indicate the 4WD position.Thus, no separate 4WD position indicator means as used in conventionalsuch assemblies is necessary. The hub clutch assembly according to thisinvention is thus simple in structure and less expensive.

What is claimed is:
 1. A hub clutch assembly comprising:a driving memberto be coupled to an axle; an outer ring coupled to a wheel hub androtatably mounted around said driving member so as to be selectivelydriven by said driving member, said outer ring having a closed end, saiddriving member being axially movable between a first position in whichsaid driving member is in engagement with said outer ring and a secondposition in which said driving member is not in engagement with saidouter ring; a movable wall fixed to said driving member and definingfirst and second variable-volume air-tightly sealed chambers in saidouter ring; first and second fluid passages for connecting said firstand second chambers to external pressure sources, respectively; a springbiasing said movable wall and thus said driving member toward one ofsaid first and second positions; a permanent magnet for magneticallyattracting said movable wall toward said closed end of said outer ring,thereby biasing said driving member toward the other of said first andsecond positions; and a pressure gauge provided in at least one of saidfirst and second fluid passages for measuring pressure in at least oneof said first and second fluid passages to determine whether saiddriving member is in engagement with said outer ring.
 2. A hub clutchassembly as claimed in claim 1, further comprising:timer-activatedvalves for respectively opening said first and second fluid passages fora predetermined time period.
 3. A hub clutch assembly as claimed inclaim 1, further comprising:a bearing supporting said wheel hub; andwherein one of said first and second fluid passages is formed partiallyby a space in said bearing.
 4. A hub clutch assembly as claimed in claim1, whereinsaid permanent magnet is fixed to said closed end of saidouter ring.
 5. A hub clutch assembly as claimed in claim 4, furthercomprising:a bearing supporting said wheel hub; and wherein one of saidfirst and second fluid passages is formed partially by a space in saidbearing.
 6. A hub clutch assembly as claimed in claim 5, furthercomprising:timer-activated valves for respectively opening said firstand second fluid passages for a predetermined time period.
 7. A hubclutch assembly as claimed in claim 4, furthercomprising:timer-activated valves for respectively opening said firstand second fluid passages for a predetermined time period.